Cloud Computing

1. Cloud Computing Cloud Network Che-Rung Lee NTHU CS5421 Cloud Computing

2. Outline • Ｎetworkoverview • Data center network • Network virtualization NTHU CS5421 Cloud Computing

3. Protocol Stack NTHU CS5421 Cloud Computing

4. Ethernet • A computer networking technology for local area networks (LANs) • Introduced in 1980. (CSMA/CD) • Standardized in IEEE 802.3 • Shared media protocol • Media: coaxial cable, twisted pair, and fiber optic • Equipment: repeater, hub, bridge and switch NTHU CS5421 Cloud Computing

5. Ethernet Frame • Ethernet switches forward “Ethernet frames” based on the 6-byte MAC address • Ethernet Address • e.g., 0-0-0a-0b-de-3e • Assigned by Ethernet hardware vendors • No geographical or organizational association NTHU CS5421 Cloud Computing

6. Switched Network • For a median or large LAN, multiple switches are connected as a graph • Problem: Broadcast Storm • Solution: spanning treeprotocol NTHU CS5421 Cloud Computing

7. Spanning Tree Protocol • Select a root bridge (switch) • Each switch determines the least cost paths to the root bridge. • The port is called“root port” • Other non rootports are disabled NTHU CS5421 Cloud Computing

8. Link-state Routing Protocol • A routing protocol used in packet switching networks. Examples include OSPF and IS-IS. • Every node (switch) constructs a map of the connectivity to the network, in the form of a graph, showing which nodes are connected to which other nodes. • Each node (switch) independently calculates the next best logical path from it to every possible destination in the network. NTHU CS5421 Cloud Computing

9. Virtual LAN (VLAN) • To reduce the amount of broadcast traffic, layer 2 switch can segment a LAN into Virtual LANs. • Members of a VLAN can only talk to other members of the same VLAN NTHU CS5421 Cloud Computing

10. IP v4 • IP routers forward “IP packets” based on the 4- byte IP address in the packet header • IP Address (e.g., 140.114.87.5) • Statically or dynamically assigned by ISPs • Geographical or organizational association • Use port number to distinct different applications(140.114.87.5:23) NTHU CS5421 Cloud Computing

11. Network Address Translation • 32 bits IP address can only offer 4,294,967,296 unique addresses. • Network Address Translation (NAT) creates new private IP addresseswithin a LAN • Ex: Each computer on the private network is translated to the same IP address (213.18.123.100), but with a different port number assignment. NTHU CS5421 Cloud Computing

12. Virtual Private Network (VPN) • A private network that uses a public network to connect remote sites or users together. • Two major components • Network Access Server(NAS) • Client software • Tunneling: place a package within another package NTHU CS5421 Cloud Computing

13. Outline • Ｎetworkoverview • Data center network • Network virtualization NTHU CS5421 Cloud Computing

14. Data Center Architecture NTHU CS5421 Cloud Computing

15. Conventional DC Network Core Aggregation Edge NTHU CS5421 Cloud Computing

16. Rack Machines • General configurations • Each rack contains 40 machines interconnected by a top of rack (ToR) switch • A standard ToR switch contains 48 GigE ports and up to 4 available 10 GigE uplinks. • Links from ToRs: Typically 1:5 to 1:20 oversubscribed (i.e., 1 to 4 Gbpsof up-link for 20 servers) NTHU CS5421 Cloud Computing

17. Requirements of Cloud Network • Mult-tenancy • Multiple virtual data centers share a single physical data center • Any server can be assigned to any service with whatever IP address the service expects • Features like link-local broadcast, on which many legacy applications depend, should work. • Virtual machines should be able to migrate to any server while keeping the same IP address NTHU CS5421 Cloud Computing

18. Additional Requirements • Uniform high capacity: • The maximum rate of a server-to-server traffic flow should be independent of network topology. • Performance and fault isolation: • Traffic of one service should not be affected by the traffic of any other service, just as if each service was connected by a separate physical switch. • Using low cost commodity network equipment only NTHU CS5421 Cloud Computing

19. Traffic Shaping • The control of computer network traffic in order to optimize or guarantee performance • Averagebandwidth • Peak bandwidth • Burst size • Load balancing policies • Ex: Leaky bucket • To check that data transmissions conform to defined limits on bandwidthand burstiness. NTHU CS5421 Cloud Computing

20. Problems of Existing Networks • LAN (layer-2 network) is not scalable and it does not allow multiple paths • IP-based network (layer 3) is scalable, but machines cannot be tied to IP addresses. • Any VM may migrate to any physical machine. • Migrating VMs should not have to change their IP addresses and all pre-existing TCP. NTHU CS5421 Cloud Computing

21. Multi-path • For (1) fault tolerance, (2) bandwidth, or (3) improved security. • Overlapped, edge-disjointed or node-disjointed • Within a layer-2 domain, the Spanning Tree Protocol causes only a single path to be used even multiple paths between switches exist. • In the layer-3 portion, Equal Cost Multipath can use multiple paths to a destination if paths of the same cost are available. NTHU CS5421 Cloud Computing

22. ECMP • Multipath routing is a per-hop decision which is limited to a single router. • Increase usable bandwidth • Performance is susceptible to changing latency, packet reordering, etc. • Equal-Cost Multi-Path routing is a routing strategy when multiple “best pathes” are available. • One way is using hashing function to selection the routing. NTHU CS5421 Cloud Computing

23. Multihoming • Multihoming: multipath provided by different ISPs • To increase the reliability of the Internet connection for an IP network. NTHU CS5421 Cloud Computing

24. Outline • Ｎetworkoverview • Data center network • Network virtualization NTHU CS5421 Cloud Computing

25. What Are Not Virtualized Yet? • Current network protocol stack makes network virtualization easy. • However, some issues need be solved • Networks of VMs within a Hypervisor • Virtual network across WAN • Some network devices, such as Infiniband • In addition, for scalability and performance consideration, some virtualization techniques need be improved. NTHU CS5421 Cloud Computing

26. Scenario 1 • Multiple LAN within a physical machine and/or across multiple physical machines. PM 1 PM 2 VM1 LAN1 VM2 • LAN1 VM3 • LAN2 VM4 • LAN1 VM5 • LAN2 VM6 • LAN2 Virtual switch 2 Virtual switch 3 Virtual switch 1 Physical switch NTHU CS5421 Cloud Computing

27. Scenario 2 • Multiple VLAN within a switched based network. LAN2 LAN2 LAN1 Switch 2 LAN1 LAN2 Switch 3 Switch 1 LAN1 LAN2 LAN1 NTHU CS5421 Cloud Computing

28. VLAN Tagging (IEEE 802.1Q) • The VLAN tag is of 2 bytes in length • The first 3 bits indicate user priority. • A canonical format indicator (CFI) bit indicates the MAC format. • The last 12 bits of the tag is for a VLAN identifier (VID), which means 4096 VLANs can coexist. NTHU CS5421 Cloud Computing

29. VLAN Trunking Protocol NTHU CS5421 Cloud Computing

30. Scenario 3 • A VLAN across WAN • Why VPN is not enough? • How about VM migration? Internet Gateway Gateway NTHU CS5421 Cloud Computing

31. References • Wikipedia • Multipath, VLAN tagging and trunking, • Photos are from the Internet • DrTzi-ckerChiueh‘stalk • Network Design Issues for Cloud Data Centers (2011-11-02 at NTHU) • Dr H. T. Hung’s talks • http://research.microsoft.com/apps/pubs/default.aspx?id=80693 • http://ccr.sigcomm.org/online/?q=node/503 • http://ccr.sigcomm.org/online/?q=node/501 NTHU CS5421 Cloud Computing